Skip asset pre-compilation when deploying if the assets didn't change

deploy.rb

namespace :deploy do
  namespace :assets do
    task :precompile, :roles => :web, :except => { :no_release => true } do
      begin
        from = source.next_revision(current_revision) # <-- Fail here at first-time deploy because of current/REVISION absence
      rescue
        err_no = true
      end
      if err_no || capture("cd #{latest_release} && #{source.local.log(from)} vendor/assets/ app/assets/ | wc -l").to_i > 0
        run %Q{cd #{latest_release} && #{rake} RAILS_ENV=#{rails_env} #{asset_env} assets:precompile}
      else
        logger.info "Skipping asset pre-compilation because there were no asset changes"
      end
    end
  end
end

Good tips!
I think Gemfile.lock should be also checked because some gems provide assets.